First REW in room Measurements. How do they look?

[MetalDaze]

As the title states this is my first foray into taking actual room measurements. I'm a firm believer in room acoustics, speaker and listener positioning, distances from walls and speaker boundary interfaces.

I'm using a UMIK-1 ver2 on a boom stand. USB into my HP Envy Tower --> USB RME ADI-2 DAC fs --> Parasound P5 --> Parasound A21+ --> Ohm I
The calibration file was downloaded and input into REW for all measurements. Microphone at ear level facing towards speakers.

The speakers are on isolation feet and sit 41.5" from the front wall. My seated critical listening position is 8.5' equidistant from the 2 speaker faces.

The room is 14' long by 11.5' wide by 8.5' tall. I'm going to call it fairly heavily treated. I have a mix of DIY, Acoustimac and GIK products for a total of 25 panels. All surfaces/main reflection points including the ceiling are covered with either a DIY 2' x 4'x 2" thick OC 703 or GIK 242 panels. There are also smaller Acoustimac 703 products sprinkled here and there. In all ceiling corners and long wall meetings there are GIK 244 bass traps, with the exception of the entry corner with the door. There is one GIK Monster Bass Trap straddled catty corner above the door. Further DIY 4' x 2' x 4" Rockwool bass traps are on the floor-wall corners on the left and right sides of the room, and floor rear wall corner.

I've done all the treatments by ear thus far and have been satisfied with the results. But before going any further or spending any more money I realized it would be smarter to start taking measurements. I am trying to evaluate my current space to see whether or not further treatments may be needed. And if so what type (tuned membrane bass trap?) Or if adding a subwoofer like the Rythmik F12 to help augments those lowest octaves as well as offset some room modes may be better. Or maybe nothing at all!

I've followed the guides in this forum and looked over other's measurements. I've also watched vids on Youtube from GIK and Audioholics. So I think I've taken the measurements correctly. I took 18 in total. 2 different positions. 3 measurements per position. And then 3 each at that same position again, for each individual speaker. I set the target SPL @75 db with a meter APP on my Samsung smartphone. Looking at the results, I think they look pretty great. But I don't fully understand what I'm looking at. Especially the waterfall graph. Any input on what/how I've measured, and what I may need to fix or remeasure would be much appreciated. Thanks!

*Edit: I've replaced the waterfall in this post with a more accurate measurement posted later here by me, which includes a time reference. The previous graph was erroneous.

 

[MetalDaze]

Here is a picture of the front part of the room for reference. Before I hooked the floor standers up.
Also no timing reference was used in these measurements (not sure what difference that makes). And all the speaker mid bass/tweeter switches were in the 0 db position.

 

[Doodski]

Wowowow. You are certainly harder-core on the room treatment. I bet that sounds good. I usually just placed a couple of panels right behind my head and call it a day and enjoy the improved imaging but you have taken it to the next level.

 

[ernestcarl]

AustinJerry at the AVSForum has a very good PDF guide to using REW: https://www.dropbox.com/s/51jpnxet3bvew2k/REW 101 HTS Current Version.pdf?dl=1

Just a few quick comments:

The phase trace looks unclear in many people's measurements. It's better if you measure per channel rather than L+R as the latter requires precise placement where the distance between the microphone and both speakers' tweeter are as good as can possibly be.

And since you are using a UMIK, you need to enable 'adjust clock' option in the analysis preference tab.

And use a time reference:

If your room has a good amount of treatment you might see a clearer phase trace as well even after simple smoothing:

I prefer to use the vector average of Lt and Rt channel measurements.

If there are any unwanted wrap arounds in the phase trace, you can use frequency dependent windowing to removing additional reflection effects.

*Cleared up the phase. Though you can still see the kink at 450Hz clearly.


I also prefer to use REW's built-in image capture tool.

For waterfall plots to check prolonged ringing, I like to use measurements where the calibrated SPL is at ~85dB.

*Used 50dB/decade in capture tool.

A vector average will not give you an accurate picture here so I prefer to use either channel or both summed.

 

[MetalDaze]

Wowowow. You are certainly harder-core on the room treatment. I bet that sounds good. I usually just placed a couple of panels right behind my head and call it a day and enjoy the improved imaging but you have taken it to the next level.

I'm a bit OCD I admit Lol Thank you. In my humble opinion it does sound and feel very satisfying

 

[MetalDaze]

AustinJerry at the AVSForum has a very good PDF guide to using REW: https://www.dropbox.com/s/51jpnxet3bvew2k/REW 101 HTS Current Version.pdf?dl=1

Just a few quick comments:

The phase trace looks unclear in many people's measurements. It's better if you measure per channel rather than L+R as the latter requires precise placement where the distance between the microphone and both speakers' tweeter are as good as can possibly be.

And since you are using a UMIK, you need to enable 'adjust clock' option in the analysis preference tab....

Thank you! the link and pictures are very helpful. There's a good amount of info to digest so I'll post back soon with new measurements.

Cheers!

 

[MediumRare]

May I suggest you expand your vertical axis to range from about 40 to 90 dB and use 1/6 or 1/12 Octave smoothing so we can see what is really happening to your FR. Also, how far apart are your speakers (tweeter to tweeter) and how far are the tweeters from your ears?

 

[MetalDaze]

May I suggest you expand your vertical axis to range from about 40 to 90 dB and use 1/6 or 1/12 Octave smoothing so we can see what is really happening to your FR. Also, how far apart are your speakers (tweeter to tweeter) and how far are the tweeters from your ears?

No problem I'll adjust the Y axis so we get a clearer view. Should I adjust both the Frequency response and the waterfall graph?

The speakers are ~ 6' apart tweeter to tweeter. ~ 3' from the side walls. 41.5" from the front wall and 8.5' from my listening spot.
The microphone was placed 46" from the back wall for these measurements (in my critical listening area) unless otherwise noted.

 

[MediumRare]

No problem I'll adjust the Y axis so we get a clearer view. Should I adjust both the Frequency response and the waterfall graph?

The speakers are ~ 6' apart tweeter to tweeter. ~ 3' from the side walls. 41.5" from the front wall and 8.5' from my listening spot.
The microphone was placed 46" from the back wall for these measurements (in my critical listening area) unless otherwise noted.

Re: The waterfall graph, yes, but for a different reason. You are looking for resonances and anything below 40 dB will not be audible anyway.

Regarding speaker placement, I've always read about equilateral triangles. It's only a guide because the directivity of your speakers and degree of toe-in are also factors. Does anyone have fact-based guidance for speaker toe-in? I have yet to find anything other than shibboleths for speaker placement. You seem to be a student of that. How did you decide?

 

[MetalDaze]

Re: The waterfall graph, yes, but for a different reason. You are looking for resonances and anything below 40 dB will not be audible anyway.

Regarding speaker placement, I've always read about equilateral triangles. It's only a guide because the directivity of your speakers and degree of toe-in are also factors. Does anyone have fact-based guidance for speaker toe-in? I have yet to find anything other than shibboleths for speaker placement. You seem to be a student of that. How did you decide?

Okay very good. I'm setting up to start taking some new measurements now.

The equilateral triangle was the golden adage I first became aware of when it came to speaker and listener placement. But as you said it really is much more of guide than a steadfast rule. The shape and size of my room predicated where and how I could place my speakers. Another guide is the "rule" of 1/3's. So the speakers should be 30% of the way into the room, and your primary listening spot should also be somewhere around 30% into the room opposite your speakers. Again, dribble if you have WAF to account for or any other number of real life scenarios.

To be perfectly honest, I found the speaker position and degree of toe in through many hours of critical listening and minor adjustments. So much so that my "bookshelf" speakers behind the floor standing ones could come down to open up the sound stage further. But I spent so much time tweaking their position. And being on foam risers I'm not sure even marking would get them back to their exact spot when I go to use them again. Each room and system is going to have it's own set of parameters.

I only just got the UMIK-1 and REW the day before yesterday. So all my treatments, speaker positioning, degree of toe and listening spot were done by ear. Science was involved too like the mirror trick for first reflections, and lots of research on room acoustics and physics. But ultimately listening to music I know really well, and then making tweaks according to what my ears told me got the job done so far.

 

[Hipper]

Congratulations on attempting this! Please don't get depressed with any of my comments but look it as a challenge to get the best possible sound from your system.

From looking at the panels you've used I think what you've probably done so far is to dampen mostly the mids and highs (various side wall and ceiling reflections perhaps) which will have given a 'drier' sound which will appeal to you. I wouldn't have thought you will have done much to tackle the bass issues. You need pretty big bass traps (such as the GIK Soffit Traps which I use) to make some progress here. I did something similar when I started on this road. I used Auralex foam products, lots of them. What I didn't realise was that they mostly do not absorb below 125Hz. What I heard seemed better, but it was not that good when I compare it to what I achieved later when I started using GIK products and measuring with REW. Now I know what a real difference controlling bass can achieve and it is worth all the effort to get it right.

That's the key point. You must control the bass region before attempting anything else. It is vital to getting the best from your equipment in your room.

To start with, so we can see where you are with this, instead of looking at the whole frequency response (FR) I suggest you concentrate on, say, 0-500Hz. This is because it is not only the hardest area to correct but also the most important. Could you please post an FR, using the 'All SPL' tab in REW. Use 'no smoothing' and as small a range of dB on the FR graphs to get the information in.

Ultimately we want to make this area as flat as possible. To achieve this you can use a range of tools - positioning, room treatment, DSP or EQ, and subs or multiple subs - whatever is convenient for you. I used positioning, lots of room treatment and EQ - my results are here, post 60:

https://www.audiosciencereview.com/.../share-your-in-room-measurements.13540/page-3

I wouldn't fuss about phase as it seems to me that when you correct the FR the phase improves along with it. More important seems to be decay times. The waterfall plots help display this but again I suggest just concentrating on the 0-500 Hz. Another display for decay times is the spectogram which you'll see on my post linked above. This is what gets you the 'tight' bass instead of a more boomy one. Again decay times come down naturally with room treatment (they may do with subs too - I have no experience of this).

Once the bass is sorted out, the mids and highs can be heard more clearly. These should not be micro adjusted like bass frequencies but more like using tone controls, using a wider range of frequencies (called 'Q').

I've never used tuned membrane bass traps but I'm wary of them. It seems to me you not only need to find the problematic bass frequency but also where to place the tuned trap to have the best effect. That isn't so easy.

 

[MetalDaze]

Congratulations on attempting this! Please don't get depressed with any of my comments but look it as a challenge to get the best possible sound from your system.

From looking at the panels you've used I think what you've probably done so far is to dampen mostly the mids and highs (various side wall and ceiling reflections perhaps) which will have given a 'drier' sound which will appeal to you. I wouldn't have thought you will have done much to tackle the bass issues. You need pretty big bass traps (such as the GIK Soffit Traps which I use) to make some progress here. I did something similar when I started on this road. I used Auralex foam products, lots of them. What I didn't realise was that they mostly do not absorb below 125Hz. What I heard seemed better, but it was not that good when I compare it to what I achieved later when I started using GIK products and measuring with REW. Now I know what a real difference controlling bass can achieve and it is worth all the effort to get it right.

That's the key point. You must control the bass region before attempting anything else. It is vital to getting the best from your equipment in your room.

To start with, so we can see where you are with this, instead of looking at the whole frequency response (FR) I suggest you concentrate on, say, 0-500Hz. This is because it is not only the hardest area to correct but also the most important. Could you please post an FR, using the 'All SPL' tab in REW. Use 'no smoothing' and as small a range of dB on the FR graphs to get the information in.

Ultimately we want to make this area as flat as possible. To achieve this you can use a range of tools - positioning, room treatment, DSP or EQ, and subs or multiple subs - whatever is convenient for you. I used positioning, lots of room treatment and EQ - my results are here, post 60:

https://www.audiosciencereview.com/.../share-your-in-room-measurements.13540/page-3

I wouldn't fuss about phase as it seems to me that when you correct the FR the phase improves along with it. More important seems to be decay times. The waterfall plots help display this but again I suggest just concentrating on the 0-500 Hz. Another display for decay times is the spectogram which you'll see on my post linked above. This is what gets you the 'tight' bass instead of a more boomy one. Again decay times come down naturally with room treatment (they may do with subs too - I have no experience of this).

Once the bass is sorted out, the mids and highs can be heard more clearly. These should not be micro adjusted like bass frequencies but more like using tone controls, using a wider range of frequencies (called 'Q').

I've never used tuned membrane bass traps but I'm wary of them. It seems to me you not only need to find the problematic bass frequency but also where to place the tuned trap to have the best effect. That isn't so easy.

Thank you! No worries I am here to polish my skills and critiques are a big part of it.

I don't have any GIK soffit or Tri-traps. But I do have:
(4) GIK 'Narrow' 244 Bass Traps @ 5.25'' thick - One with range limiter opposite the monster on front wall
(1) GIK 24'' x 36'' Monster bass trap 7 1/2" thick
(2) Acoustimac 48'' x 12'' Bass trap 4" thick
(2) DIY 24" x 48" x 4" Rockwool Bass traps
(2) DIY 12" x 48" x 4" Rockwool Bass traps

Other speakers I've had sounded very good in this room and setup. But the floor standing speakers are probably just plain too big for this room. But I love the bass and dynamics. So I'm sort of shoe horning them in with acoustic treatments as lubricant Lol.

The rest of the panels for the mid bass and highs are:
(3) GIK 242 Panels on cloud brackets (3.5" thick)
(2) Acoustimac 2' x 2' x 2" OC 703
(2) Acoustimac 1' x 2' x 2" OC703
(4) GIK Alpha Panels with diffusors
(6) DIY 4' x 2' x 2" OC703

I was trying to avoid the room sounding dry. I am aiming for really tight, clean bass. With decay times to match. I was looking to get the room RT60 down to 0.5 or 0.4. But I do not want a muffled or rolled off high end. My hearing is still good out to 16K Hz but I also want to attempt to keep it that way for as long as I can.

I'm right there with you. I like GIK products and was surprised to see how much mass is needed to absorb frequencies below 150Hz. I'm redoing some measurements now so I will also look into what you posted about spectrograms. Your waterfall graph is nice and clean, and basically what I am shooting for as well. Remarkable to see the difference treatments make in the before and after measurements!

The 85db waterfall sweeps I did for both and individual channels I ran from 10-200 Hz. So I will take a few more measurements now and run them up to 500Hz as you suggested

 

[Hipper]

You can still use your previous measurements even if they were from 0-20KHz. Just alter the graph sizes using the 'Limits' and 'Controls' buttons, top right of the FR graph..

 

[MetalDaze]

Ah, I see that now. Well I can always use more practice running measurements. Acoustic timing reference used.

Here is the FR from 10-500Hz with no smoothing. L+R 40 to 100dB.

Here is the waterfall for L+R 10-500Hz scaled from 40 to 95dB. Target 85dB. Acoustic timing reference used.

 

[MetalDaze]

Here Is the FR plot from 40 to 95 dB with 1/6 octave smoothing. Acoustic timing reference used. Target 75 dB.

And here is a waterfall plot of just the left channel. Target 85dB. There is some more ringing on this channel since the exterior wall closest to this speaker is brick. The wall behind the speakers is double block concrete. The wall to the right of the speakers is plaster over lathe with sheet rock atop. And the rear wall is sheet rock with a closet which has been filled to the brim with misc. storage.

I am on the second story so it is a suspended floor (hence the isolation pucks) and the ceiling is 3/8" drywall with R19 insulation bats on top. There is another 10 feet or so above my ceiling to the bottom of the roof.

 

[MetalDaze]

And finally here is the spectrogram for both L+R speakers. 10-500Hz

 

[escape2]

View attachment 107245
Here is a picture of the front part of the room for reference. Before I hooked the floor standers up.
Also no timing reference was used in these measurements (not sure what difference that makes). And all the speaker mid bass/tweeter switches were in the 0 db position.

I take it you're not married?

 

[MetalDaze]

I take it you're not married?

Ha! I was waiting for this comment I'm engaged to be married in a few months.

She's a wonderful woman who has been with me every step of the way. And I almost always run an idea by her before I act on it. I'm very lucky to have her and as they say, happy wife happy life!

PS I should add we've been together for almost a decade and have lived together since college. Covid & quarantine just gave me the time to really go crazy on the listening room.

 

[MediumRare]

Looks like knocking down those nodes at ~47 Hz and ~110 Hz with some EQ could do you a world of good, might help your nulls as well.

 

[MetalDaze]

Looks like knocking down those nodes at ~47 Hz and ~110 Hz with some EQ could do you a world of good, might help your nulls as well.

I have the ability to play with the EQ in the ADI DAC so I'll have to try some tweaks and measure the response.

The only thing that bugs me about that is, in my use case, I like to leave the DAC in DSD Direct unless I'm listening to headphones. Which disables all EQ and tone control functions. I do this for the purity of the signal chain, and because I have a fairly large amount of digital music in both DSD and high rate PCM. I'll have to try it with the EQ and see. It may sound noticeably better to where I wouldn't want to listen without it.

My alternate route if not adding further bass trapping would be a subwoofer (or 2 but I'm short on space). I'd be interested to see what the FR curve would be running my speakers full range and implementing a rythmik sub perhaps out of phase with the speakers. Crossing the sub in around the second problem peak and running it down to 20Hz.